1. Technical Field
The present invention relates to an integrated gasification apparatus for carbonaceous fuel including a flash dryer.
This application claims the benefit of priority No. KR 2012-0153791 filed on Dec. 26, 2012.
2. Description of the Related Art
In order to produce electricity, chemical materials and synthetic fuel or to achieve a variety of applications thereof, fossil fuel such as coal may be gasified. Gasification indicates production of a syngas that is made up of carbon monoxide and hydrogen via incomplete combustion of hydrocarbon fuel and oxygen at very high temperature, so that the produced gas has higher efficiency than that of original materials and may be discharged in the form of a material that causes less environmental pollution.
Carbonaceous fuel is typically dried before gasification. This is because fuel having low water content may be more easily combusted and may be more efficiently gasified. However, the case of using fuel having high water content such as low-grade coal and biomass is problematic because high costs are required to remove water and it is difficult to perform gasification with the presence of water. For example, biomass such as corn stalk has such high water content that it is inefficient for fuel gasification. When carbonaceous fuel having high water content is used, such water in fuel may decrease fluidity and may frequently incur plugging during handling and transport of the fuel, and high costs and energy are required to remove water from the fuel.
In order to lower water content of fuel to improve gasification efficiency, a large amount of heat should be transferred to a drying target, and thus a dryer should be made so as to have the shape and size adapted therefor. Currently, limitations are imposed on lowering the water content of fuel having high water content via heat supply and retention time in a typical atmospheric dryer, undesirably decreasing efficiency of the gasification apparatus.
In the case when steam produced through heat recovery during the gasification process is indirectly used as a heat source of a dryer, the cost for a heat exchanger is additionally required. Furthermore, gas discharged from the dryer after treatment of carbonaceous fuel may be emitted to the atmosphere only after passing thorough heat recovery and purification facilities, and thus the facility cost therefor is also additionally required.
The syngas produced through the gasification process is subjected to a purification process and a reforming process to produce chemical products or synthetic fuel. The purification process enables materials such as fine powder, sulfur, mercury, carbon dioxide, etc. to be removed from the syngas, and the reforming process makes the composition of the syngas adjustable. As such, the H2/CO ratio in the syngas is regarded as important to produce chemical products, and the required value thereof varies depending on final products. For example, in the case of a Fischer-Tropsch (F-T) process, the H2/CO ratio should be set to 2:1.
The process of adjusting the H2/CO ratio is typically exemplified by a water gas shift process, which carries out the reaction of the following Scheme 1 using a catalyst under high-pressure conditions (e.g. 12˜30 bar).

The water gas shift process may be classified depending on the conditions of catalyst used, and is largely divided into a sour shift process (about 270˜510° C.) and a sweet shift process (about 177˜316° C.) depending on whether syngas before or after removal of impurities such as H2S therefrom is used. Individual processes are favorable in terms of decreasing the equilibrium concentration of CO and increasing the reaction rate in proportion to an increase in concentration of H2O. Hence, in the case when the concentration of H2O in the syngas is not sufficient, steam may be added to the process so as to increase the conversion of CO. However, supply of high-pressure steam increases the process costs.
In the gasification process, additional high-pressure steam may be needed in the water gas shift reaction able to increase the H2/CO ratio. However, to produce such high-pressure steam, additional water resources and water purification/heat exchange facilities are required.